Thermoplastics comprise a large body of commercially important products. Among the uses of thermoplastics are those in which the optical properties of the polymer are important, particularly when the polymer is an optically clear material with little distortion of optical images. Such polymers, for example poly(methyl methacrylate) (PMMA) and certain polycarbonates are used as substitutes for glass where toughness is important. In uses such as for safety glazing and signage, other properties such as weather and/or heat resistance may also be important. For example if such a part needed to be thermally sterilized, it must withstand the temperature of the sterilization process. Polycarbonates often have poor weathering and/or hydrolysis resistance, while PMMA has a relatively low glass transition temperature (Tg), so its heat resistance is poor. Thus polymers with a combination of good optical properties, and heat and weathering resistance are desired.
The polymers of certain α-methylenelact(ones)(ams) (AMLs) have the combination of good properties, but often are quite brittle, see for instance U.S. Pat. No. 5,880,235, and the discussion at columns 1–3, and D. Arnoldi, et al., Kunststoffe, vol. 87, p. 734–736 (1997). Thus if one could toughen these polymers without compromising their other superior properties, useful compositions would result.
While the toughening of AMLs using toughening agents is in the Applicant's knowledge not reported in the literature, toughening of thermoplastics in general using toughening agents is known. For example, poly(meth)acrylates have been toughened by a number of methods, see for instance U.S. Pat. Nos. 5,625,001 and 5,998,554, and World Patent Application 99/12986.
Tougheners for various types of engineering resins [including (meth)acrylics] and other polymers are sold by Rohm and Haas Co., Philadelphia, Pa., U.S.A. under the tradename Paraloid®, such as their EXL™ series which is believe to be a core-shell polymeric particle product with a rubber core and thermoplastic shell, and also see for instance U.S. Pat. Nos. 3,678,133, 3,793,402, 3,808,180, 3,985,703, 4,180,494, and 4,543,383.
Other types of thermoplastics have been toughened by the addition of elastomeric polymers which contain reactive groups such as epoxides, see for instance U.S. Pat. No. 4,753,980.
Conversely, AMLs may be used to improve the properties of thermoplastics, including thermoplastics containing functional groups which potentially may react with the AML. Such thermoplastics include polyamides, polyesters, and polyacetals, and nonfunctional group containing thermoplastics such as styrene/acrylonitrile copolymers. It is believed that to be most effective in improving properties, the AML should be dispersed within a matrix of the thermoplastic. Polymer-polymer blends of various polymers are well known in the art, but to Applicants' knowledge, no blends of AMLs with other polymers have been reported.